When I took Benadryl to help my insomnia while I was hyper and even when my numbers were normal on methimazole, I woke up with a racing heart (especially when I was hyper). I believe novacaine & ephedrine have the same effect on someone with Graves. I have read a few articles on line that people with hyperthyroidism should be “wary” (as it was put in a nursing article) using antihistamines. My endo told me to take the Benadryl when I was dealing with insomnia while I was hyper, but the 2 nights I took it, I woke up with a racing heart and sweating. So I stopped using it.
Alexis
http://e-edcredits.com/nursingcredits/article.asp?testID=1 (That’s the article).